International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004 
  
  
  
  
  
  
  
  
  
(1) Sketch map 
Figure 6 the disposal of dangle ed 
oe 
A/Ay, — (A90) A (A90) A (Avi) 
2-Ay/Ax, (A>) A(A>0) A (A < Axi) 
2—-Ay/Ax, (Ay X 0) A (A70) A(Aa» — Ay) The algorithm has been tested in our experiment environment. 
4+Ax/Ayı, (Ay « 0) A (A70) ^ (^a E—Ay) The development environment is Delphi 6.0 and MapX. The 
4+A0/Au, (An <0) A (Ax <0) A (A X Ax) experiment data is the road network data within the second ring of 
6—Ay/Ax, (Ay <0) (Au «0) (A > Ax) Beijing. And the experiment is completed in the personal 
6— AWA, (A >0) A(An <0) A(Ap €x) computer that has PII CPU, 256M memory and Win2000 OS. 
8+Ax/An, (An >0)A(Au <0)A(Au >—An) 
(2) Formula 
5. EXPERIMENTS 
Qx y)- 
Table 7 is the result in comparison with the traditional methods. 
  
In the table, Ty; is the node-edge topology and Tr is the special 
à area topology. And TM represents the traditional Methods; PM 
Fig. 5 Qi Operators ; 
represents the present methods. From the experiment result, we 
know that when building the node-edge topology the time 
When searching for the next edge in the clockwise based on the 
efficiency of the present algorithm is similar with that of the 
current edge, we at first compute the value of Qi operator of every 
traditional one. But when building the area topology, the present 
edge that is related to the end node of the current edge. Then sort 
algorithm saves us much more time. Moreover, the constructed 
them ascending. If Gi; is in the front of Qi; the edge whose Qi 
? area topology is more appropriate to the ITS application. 
operator values Qi; is the next edge of the one whose Qi operator 
  
  
  
  
  
  
  
  
  
  
  
  
values Qi;. 
Time Twx (S) Tax (S) 
: Data TM PM TM PM 
The disposal of Dangle Edge: Generally speaking, the dangle 
id Edge:!104 ]" 0.9" 3" j" 
nodes should be removed before building the polygon topology. 
; : E Node..68 
But in the road network, the dangle edge is permitted, such as the 
; ee : Edgel 11,128 3" 2" 13" 4" 
dead road. Therefore, while building the special area topology, 
: re ae Node! 1736 
we should dispose the dangle edges distinguishingly to ensure 
: T Edge 112,485 12" 8" 125" 18" 
that the search process continues. In our methods, we at first 
‘ : Node/18768 
judge whether the number of the edge related to the current node 
is only one. If it is, the current edge is dangle edge. Change the Table 7 The Experiment Results 
current node to the other node of the current edge and search 
unceasingly. Fig. 6 describes the disposal process of dangle edge. 
on . DISCUSSION AND CONCLUSION 
The arrows identify the search direction. 6 
The experiment indicates that the algorithm presented in the paper 
has the following advantages. Firstly, the proposed topological 
relationships, which are composed of edge-node topology, 
node-edge topology and “special” area topology, are more 
appropriate to ITS application because they consider the 
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